If you don't have an alternative UI (speedUI, Metakernel etc) I think it is simply a matter of pushing "MTH" and scrolling through commands, and then "PRG" and doing the same thing, and etc.
That's what I do, anyway, with my limited facility in RPN.

to get the full command set as multiple pages of menu items. It's not particularly useful because it's not in alpha order, and you can't jump to particular entries, unless you count using a page number after the menu number, e.g.

2050.06 MENU

takes you to page 6 of the full listing which begins with DDAYS.

I don't have a G/GX, but reading the HP50g AUR and using an emulator, it looks like menu number 2219 will give you the additional 48G commands.

I hope my response is in the correct place,
anyways - Thanks guys for all the enlightening info!.
(Now I begin to realize how little I know about this HP device of wonders...)
P.S.
the- 2219 MENU (and 2050) work!, very Cool 'trick'. thanks.
P.P.S.
Someday, I fully intend to read the "HP Programmer's Reference Manual",
Alas, evil ninjas have stolen this ancient tome of knowledge from me.
So in the meantime I will seek wisdom in this wise (and friendly) forum. :)
Lior